Fig. 7: Comparison of choice preferences during high and low exertion efforts, controlling for the number of exertion repetitions (participants from the Main Experiment and Control Experiment 2; n = 37).

a We compared behavior during the first 25 fatiguing exertions between the main experimental group (first 3 exertion and choice blocks) and the control experimental group (first 5 exertion and choice blocks). In the main experiment participants exerted at a level of 80U, and in the control experiment participants exerted 10U. Participants did not perform a significantly different number of exertion trials between these experimental epochs (Paired t-test (two-tailed): t₃₄ = 0.08, p = 0.94). Error bars indicate SEM. b Participants exerted significantly more effort in the main experimental group compared to the control experimental group (Unpaired t-test (two-tailed) comparing the mean effort produced between groups: t₃₄ = 38.83, p < 0.001). Error bars indicate SEM. ***p = 9.44 × 10⁻³⁰. c Comparison of choice similarity metrics between the main fatigue experiment and control experiment, averaged across the selected epoch. Relative to the baseline choice phase, positive values indicate more risk-seeking behavior in the subsequent choice phase, whereas negative values indicate more risk-averse behavior. There was a significant difference between choice behavior in the main and control groups (Unpaired t-test (two-tailed), t₃₄ = 2.60, p = 0.013). Participants in the control experimental group did not significantly alter their choice behavior during 10U exertion (Unpaired t-test (two-tailed) t₁₆ = 1.61, p = 0.126), while those in the main experimental group became significantly more risk-averse for effort during 80U exertions (two-tailed one-sample t₁₈ = 2.13, p = 0.047). These results indicate that changes in choice preferences are not simply the result of the experience of repeated exertions, but instead are induced by fatigue resulting from high intensity exertion. Error bars indicate SEM. *p < 0.05.